1. Technical Environment
The object of the present disclosure is a device for preventing overfilling of containers, in particular containers intended to contain liquefied gases.
2. Prior Art
Such containers, better known as “cylinders,” are widely utilized where a connection to the distribution network for fuel gases has not been provided.
For financial and safety reasons it is best that the cylinders should be filled with a predefined maximum quantity of gas, avoiding overfilling and thus excessive internal pressure. For this reason the cylinders are equipped with devices for preventing overfilling, sized to cut off the flow of entering gas when a desired fill level has been reached.
Devices of the type described above are known, for example, to the production of the Applicant and include membrane valves. Such valves are of the type that is normally closed and include a perforated membrane in the center, which, becoming deformed under the action of the entering gas, permits its passage. The gas flow is intercepted when a prearranged level of filling is reached and a piston, placed below the membrane and actuated by a cam connected to a float inside the container, thrusts against a seat, closing one section for passage of the gas. The variation of the sections for passage causes a counter-pressure that acts on the membrane in a direction opposite to that of the gas entering the container, closing the entrance orifice.
The disadvantages of such solutions are those typical of the applications of valves to membranes, i.e., the greater predisposition to wear and tear and the consequent lesser reliability compared to solutions that use valves in which the closure means is a rigid component.
Another inconvenience encountered in the specific application of the device for preventing overfilling of cylinders is represented by the fact that the membrane valve thus conceived makes it difficult to produce a vacuum inside the container.
A further drawback encountered is the reduction of the capacity of exiting gas during normal use.
Devices for preventing overfilling of cylinders that employ valves without membranes are known, for example, from the American patent U.S. Pat. No. 4,541,464. In this solution the valve is spherical, normally open. The obstructing sphere is kept in the open position by means of a pin constructed on a spherical member connected to a float by means of a cam driver. During the filling operation the float comes out of the container so that it causes the spherical member to rotate by means of the driving action of the cam. The system is sized in such a way that when the filling position is reached, the rotation of the spherical member causes a loss of contact between the pin and the sphere, which is thrust into the closed position of the valve by the force of gravity, besides a possible return spring.
A principal drawback of such solutions is represented by the fact of its being sensitive to the inclination and the oscillations of the cylinder, also from the moment that the spherical member rotates as an effect of any kind of deviation of the cylinder's axis from the vertical position.
A second problem is represented by the sluggish speed of the system once the maximum fill level of the cylinder has been reached.
A further problem with this solution is determined by the number of elements that compose it and the use of spherical members that complicate the operations of construction and assembly, making the device particularly sensitive to size tolerances and coupling. For the same reasons, the reliability of this solution in use is limited.